Efficacy of Fluorescence Microscopy in the Diagnosis of Tuberculosis in Guyana

Abstract

Background: Tuberculosis is one of the potentially serious human diseases and is still one of the major causes of mortality. It ranks as the second most leading cause of death from a single infectious agent, after the human immunodeficiency virus (HIV). Objective: The aim of the study was to evaluate the efficacy of Fluorescence microscopy (FM) technique to determine sensitivity in detecting TB between HIV positive and HIV negative patients in a poor resource country. Methods: The study was a cross sectional and blind assessment on 50 suspected cases of TB among HIV positive and HIV negative patients using FM method against Zeihl Neelsen (ZN) staining method. Culture results were considered as gold standard. Results: Of the total 50 specimens examined by ZN, FM and culture method 32%, 40% and 38% were found positive by ZN, FM and culture respectively. FM was sensitive to ZN on several aspects. The difference in their case detection rates were statistically significant (X2 = 35.3, p<0.001). In detecting overall patients for TB, FM method showed sensitivity of 90.0% (95% CI 68.3-98.5) over ZN method 75.0% (95% CI 50.9-91.3) with a kappa value of 0.83 (p≤0.05). FM method showed excellent sensitivity, sensitivity, PPV and NPV all with 100% (95% CI 48.0-100) among HIV-TB patients and an excellent kappa value of 1 (p≤0.05). Conclusion: This study presented greater sensitivity of FM method over conventional ZN staining method in detecting TB among HIV positive patients. Fluorescence microscopy can be widely used even in peripheral laboratories where culture facilities are not available.